Rock drill



Dec. 14, 1937. W. J. MCCALLUM I 2,101,865

ROCK DRILL Filed Feb. 18, 1935 Patented Dec. 14, 1937 UNITED STATE S PATENT OFFICE 4 Claims.

This invention relates to drills and particularly the type employed in producing holes in rock formations for the purpose of inserting sticks .of explosive.

In the mining of ores it is commonly the practice to drill holes of relatively small diameter,

say about an inch and a quarter, and of considerable depth, say or feet at spaced points throughout a particular formation and to then insert suitable charges of explosive in the holes so that a considerable quantity of the ore can be blasted out. A difficulty-encountered in these operations is that the drills are dulled very quickly even when formed of special, hard, tool steels. A drill can scarcely be used more than a minute before it requires resharpening. This means that in the course of a day a considerable number of drills are required and'there must be kept on hand a large quantity of the drills or they must be transported to and from the sharpening equipment at frequent intervals. In the use of the ordinary drilling equipment this matter oftransportation is an important item in that the drill members carrying the cutting edges are long and heavy and usually must be conveyed a considerable distance to the sharpening equipment. This equipment is ordinarily above ground while the, drilling operations may be carried on as much as 5,000 feet or more below the surface.

Attempts have been made heretofore to reduce the transportation problem to a minimum by providing a detachable bit or cutting element at the end of the drill rod but these attempts have not proved successful for one reason or another. They have ordinarily involved such an expensive construction as to make their use impracticable. Furthermore, they have usually involved the use of screw-threads at one point or another for the attachment of the cutting elements to the drill rod. This has led to difllculties in view of the tendency of the parts to unscrew and become detached in the course of handling and use. Various other diiiiculties have been encountered and accordingly these prior devices have not proved sufliciently satisfactory to justify the expense.

The present invention provides the advantages of a small, detachable bit, without the objectionable features of prior known devices. The construction is inexpensive, simple to produce, simple to employ, and thoroughly reliable in operation, enabling the use of a bit, with cutting portions formed of hard material, such as a high grade, hard steel, and with a retainer por- 55 tion of a softer, more ductile but tough material, capable of withstanding the shocks and strains to which the tool is subjected. Very simple and effective means are provided forattaching the cutting portions to the retainer and detachably connecting the retainerwlth the drill rod. No screw-threads are employed for either of these purposes, and the construction issuch that a complete bit may be produced for only a few cents. Thereby the bits may be used until they become dull and then discarded. It is possible, however, to resharpen and reuse the bits if desired, and the material in them may, in any I event, be readily salvaged and reused.

Other features and advantages of the invention will appear from the detailed description of an illustrative embodiment of the same which will now be given in conjunction with the accompanying'drawing, in which Figure 1 is an end view looking down upon the cutting edges of a bit constructed in accordance with the invention but at a stage prior to the completion of the device.

Figure 2 is a view of the same incompletely finished unit partly in side elevation, partly broken away and partly in section along the line 2-2 of Figure 1.

Figure 3 is an end view, similar to Figure 1, but of the completed unit.

Figure 4 is a view similar to Figure 2 but of the completed unit, taken partly in section along the line 4-4 of Figure 3, and showing the bit in relation to a drill rod.-

Figure 5 is a bottom view of the completed unit.

Figure 6 is a perspective view of one of the hardened cutting nibs employed in the bit, and

Figure 7 is a detail view in vertical section through the upper portion of the retainer.

Referring now to the drawing, the main body of the improved bit comprises a retaining sleeve or member l0, This is originally produced in the form indicated in Figures 1 and 2. The outer contour of the lower portion of the sleeve may appropriately be defined by a series of flat surfaces ll separated by a series of rounded comers 12. A large, central opening or passageway i3 is formed through the entire retaining sleeve and the lower portion of this opening may conveniently be formed with four flat sides It presenting a substantially square cross section with four rounded corners. The upper portion of the retaining sleeve is initially provided with a substantially circular contour I! while the interior of this portion is provided with a series of inwardly extending triangular projections l6.

These projections are such as to provide a series of four recesses opening toward tlle center of the sleeve toform a cross. Each of'these recesses is bounded on its three closed sides by walls I1, IS, and I.

The retaining sleeve may be formed of any suitable, ductile, durable material capable of withstanding the shocks and strains incident to the drilling of rock. It need not be hard or wear resista'nt, however, since none of the cutting is effected by this portion of the bit. It may ap- .propriately be formed of a low carbon, 'ductile steel containing about .15 to 30% carbon. Such a steel me;' be readily worked in the manner required by theinvention and affords a retainer that will cushion the shocks imparted to the drill in the course of drilling through rock. The sleeve may be formed in any convenient way, as by forging a suitable piece of the material or by casting the same in the desired shape or by suitably machining and otherwise forming a section of tubular stock into the desired configuration.

The cutting action of the bit is performed by a series of nibs 20 formed of any suitable, hard, cutting alloy, such as a steel having a high carbon content of between .5 and 1.5%. Each nib has its upper end provided with sloping surfaces arranged to present a ridge or cutting edge 2|, which, in the use of the bit, is brought into engagement with the rock. In the construction illustrated four of the nibs 20 are inserted in the retainer ill in such a way as to leave a square opening at the center whose sides are of somewhat smaller dimension than the width of the nibs. To permit this the inner corners of the nibs are beveled, as indicated at 22, throughout the portions that are brought into direct contact when the nibs are assembled in the manner shown. Each nib is formed with a downward extension or shank 23 which at its lower end is of substantially the same width as the distance between the surfaces l1 and IQ of the retainer. This enables the nibs to be freely inserted in the four recesses previously explained, that open into the center of the sleeve. The heads of the nibs are somewhat wider than the portions 23 and are adapted to overlie the upper surfaces of the triangular projections It as well as a portion of the surrounding wall of the retainer. As best shown in Fig. 2, the portions 23 of the nibs are not provided with parallel sides from top to bottom but are grooved or indented at the sides as indicated at 24. The purpose of this, as will be made clear later, is to provide for the anchorage of the nibs in the retainer. It is to be understood in this connection that while the depressions or indentations 24 are indicated as having a particular form, considerable latitude is permissible in the construction of the nibs. Any undercut or indented construction that will accomplish the desired anchoring may be employed. It will be understood that the length of the projection 23 in the. direction of the edge 2| is such as to allow it to fit snugly in the recess bounded by the walls l1, l8, and I9.

Upon assembling the nibs in the retainer in the manner indicated the unit is placed in a machine capable of exerting an immense pressure upon the upper portion of the retainer at the four points intermediate thepibs. The pressure is suilicient to force the metal inwardly at these points causing it to flow into the recesses or indentations 24 in the nibs and producing indentations 25 in the outer surface of the retainer. If desired the retaining sleeve may be heated prior to inserting the nibs and applying pressure. This would reduce the pressure required and increase the squeezing action upon the nibs due to the subsequent shrinking of the retainer.

It will be apparent that after the pressure has been applied the nibs will be very firmly held by the retainer. The walls l1, IL and II will be squeezed into close contact with the three adjacent sides of each nib and the beveled surfaces 22 of the several nibs will be forcibly pressed together. Accordingly there is no danger of movement of the nibs relative to the retainer in any direction.

At one of the corners l2 of the retainer and near the bottom of the latter there is provided a transverse slot 26 extending to about the middle of the two adjacent flat surfaces II. This slot forms a relatively narrow section or strip 21 adjacent the open end of the bit which may be readily pressed in to the extent indicated in Figure 4. A sharp blow by a reasonably heavy hammer will be suflicient to force the strip inwardly in this manner. The purpose of this is to enable quick and simple attachment of the bit to the end of a drill rod '28. This rod is preferably square in cross section so as to form a relatively snug fit within the opening I! of the bit. A notch 28 is formed at one corner of the rod a short distance from the end to present a shoulder 30 for cooperation with the upper edge of the strip 21. The shoulder 30 is located at such a distance from the end of the rod that when it is properly engaged by the strip 21 the end of the rod is substantially in contact with the surface 3i provided at the inner ends of the nibs 20. It will be understood thatthe, strip 21 is not forced inwardly into retaining position until after the retainer sleeve is applied over the end of .the drill rod. One way of indenting the strip 21 is to support the bit and drill stem by means of an upward projection on an anvil that engages only the strip 21 and to then strike a sharp blow at the opposite comer of the bit, but other methods may be employed. The bit may be removed by any suitable and convenient method, as for example, by inserting the ,bit in a slotted anvil having a V-notch adapted to receive the drill stem but too small to permit the e of the bit, and then imparting a quick movement to the drill stem in the direction of its axis. This will bring the inner end of the bit sharply against the wall of the anvil around the V-notch and will remove the bit from the stem. Or if desired a chisel or similar wedging implement may be driven into the space between the notch 29 and the strip 21 to pry the latter outwardly and thus enable removal of the bit or the strip 21 may be split open by means of a chisel. The bit may be discarded after removal, being scrapped and the steel being salvaged. A new hit will be applied to the drill rod as frequently as necessary to provide eflicient drilling.

An opening 32 is preferably provided along the central axis of the drill rod in communication with the opening formed between the inner ends of the cutting nibs." This allows water or air or other cooling fluid to be supplied to the cutting edges, the fluid being permitted to pass outwardly again through the channels formed by the depressions 25 and the :tlat surfaces II and thence along the entire outer surface of the rod.

While the square formation of the rod' 28 and opening l3 are preferred it will be understood that other arrangements permitting a torque to be transmitted from the rod to the retainer sleeve may be employed. For example the rod and opening might have a hexagonal or any other polygonal form, or the rod and sleeve might have interfitting splines or a key and keyway or similar interfitting projections and recesses. Furthermore, the form and arrangement of the cutting nibs and the number employed in each retainer may be varied. Various other modifications will suggest themselves to persons skilled in the art and it will be understood, therefore, that the scope of the invention is not restricted to the particular form shown, but is defined in the following claims.

What I claim is:

1. In a device of the class described a drill rod having a polygonal outer contour, a detachable bit having a socket portion with an opening of'corresponding polygonal cross section adapted to snugly fit the end of said rod and be ap plied thereto by a rectilinear sliding movement, said socket portion being formed of ductile material, cutting elements of hard, wear-resistant material firmly and permanently united with said socket portion, and inter-engaging shoulders carried directly by said rod and socket portion for retaining said parts in assembled relation, one of said shoulders being shiftable relative to the member by which it is carried into interengagement with the other shoulder, both of said shoulders then being rigidly and unyieldingly held in interengaging relation.

2. In a device of the class described a-drill rod, a bit adapted to be engaged with said ro'd by freely sliding-it rectilinearly over the end of said rod, said rod and bit having cooperating surfaces non-circular in cross-section so arranged as to transmit a torque from one to the other,

and interengaging means carried permanently and rigidly by said bit and rod and presenting interlocking shoulders positively preventing sliding movement between said bit and rod out of assembled relation, one of said means being shiftable with respect to the member by which it is carried.

3. In a device of the class described a drill rod having a polygonal outer contour, a detachable bit having a socket portion with an opening 'of polygonal cross-section adapted to snuglyfit the end of said rod and be applied thereto'by a rectilinear sliding movement, and interengaging means carried permanently by said rod and bit at one of the corners of the polygon for retaining said parts in assembled relation, one of said means comprising a part displaceable from normal into interengaging relation with the other of said means and adapted to remain rigidly in such position.

4. In a device of the class described a drill rod having a. polygonal outer contour, a detachable bit having a socket portion with'an opening of polygonal cross-section adapted to snugly fit the end of said rod and be applied thereto by a rectilinear sliding movement, a shoulder on said rod extending transversely thereof, and means carried by said bit formed and arranged to be readily pressed inwardly and remain rigidly in such position to provide a projection to cooperate with the shoulder on the rod and prevent disengagement of the parts.

. WILLIAM J. McCALLUM. 

